Supplemental oxygen is frequently used in the treatment of pulmonary insufficiency in patients with acute respiratory distress syndrome (ARDS), which is a severe form of acute lung injury (ALI), affecting millions worldwide. Hyperoxic lung injury is recognized as an appropriate model for ALI/ARDS. The central hypothesis of the research proposed in this application is that specific single nucleotide polymorphisms (SNPs) in the genes for NF-E2-related factor (Nrf2) and/or NADPH quinone reductase (NQO1) contribute to ALI/ARDS by attenuating the expression of pulmonary and hepatic functional phase II anti-oxidant enzymes, leading to increased formation of oxygen-mediated reactive oxygen species (ROS), which in turn results in increased susceptibility to ALI/ARDS, as well as exacerbated lung damage in these patients. In order to achieve these goals, we propose the following Specific Aims: 1. To test the hypothesis that humans carrying specific SNPs on the Nrf2 or NQO1 genes will be more susceptible to develop ALI/ARDS than those who do not, and these individuals will display increased sensitivity to oxidative stress than those carrying the wild type genes. Endotracheal aspirates from individuals suffering from ALI/ARDS or controls will be analyzed for the presence of SNPs, F2- isoprostanes/isofurans, levels of bulky oxidative DNA adducts, and protein oxidation products. Gene expression profiles will also be studied using RNA from tracheal aspirates of these individuals. 2. To determine the mechanisms by which mice lacking the genes for Nrf2 and NQO1 are more susceptible to hyperoxic lung injury, and test the hypothesis that the cytochrome P4501A (CYP1A) inducer [e.g., - napthoflavone (BNF)] or omeprazole (OM) will rescue the mice lacking functional Nrf2 or NQO1 genes against hyperoxic lung injury, via novel mechanisms entailing hepatic and pulmonary CYP1A enzymes. 3. To determine the mechanisms by which known SNPs on the Nrf2 or NQO1 promoter modulate oxygen toxicity in human lung cells or in humanized mice in vivo. This aim has two sub-aims. (i). To test the hypothesis that human lung cells carrying known SNPs of Nrf2 or NQO1 gene will be more susceptible to oxygen toxicity. (ii) To create transgenic humanized mice expressing the normal human Nrf2 gene or NQO1 gene or those carrying known SNPs on these genes, and determine the role of SNPs in hyperoxic lung injury. Omics' approaches, including genomics (microarrays) and proteomics approaches will be used to determine the molecular mechanisms by which Nrf2 or NQO1 variants contribute to lung injury. Successful accomplishment of the aims could lead to innovative strategies for the development of novel biomarkers as well as new approaches (e.g., use of PPI such as OM) for the prevention/treatment of ALI/ARDS in humans.